High efficiency thermionic converter studies

The objective is to improve thermionic converter performance by means of reduced interelectrode losses, greater emitter capabilities, and lower collector work functions until the converter performance level is suitable for out-of-core space reactors and radioisotope generators. Electrode screening experiments have identified several promising collector materials. Back emission work function measurements of a ZnO collector in a thermionic diode have given values less than 1.3 eV. Diode tests were conducted over the range of temperatures of interest for space power applications. Enhanced mode converter experiments have included triodes operated in both the surface ionization and plasmatron modes. Pulsed triodes were studied as a function of pulse length, pulse potential, inert gas fill pressure, cesium pressure, spacing, emitter temperature and collector temperature. Current amplifications (i.e., mean output current/mean grid current) of several hundred were observed up to output current densities of one amp/sq cm. These data correspond to an equivalent arc drop less than 0.1 eV

High efficiency thermionic converter studies

Research in thermionic energy conversion technology is reported. The objectives were to produce converters suitable for use in out of core space reactors, radioisotope generators, and solar satellites. The development of emitter electrodes that operate at low cesium pressure, stable low work function collector electrodes, and more efficient means of space charge neutralization were investigated to improve thermionic converter performance. Potential improvements in collector properties were noted with evaporated thin film barium oxide coatings. Experiments with cesium carbonate suggest this substance may provide optimum combinations of cesium and oxygen for thermionic conversion

BMQ

BMQ: Boston Medical Quarterly was published from 1950-1966 by the Boston University School of Medicine and the Massachusetts Memorial Hospitals. Pages 49-52, v17n2, provided courtesy of Howard Gotlieb Archival Research Center

The labour supply effect of Education Maintenance Allowance and its implications for parental altruism

Education Maintenance Allowance (EMA) was a UK government cash transfer paid directly to children aged 16–18, in the first 2 years of post-compulsory full-time education. This paper uses the labour supply effect of EMA to infer the magnitude of the transfer response made by the parent, and so test for the presence of an ‘effectively altruistic’ head-of-household, who redistributes resources among household members so as to maximise overall welfare. Using data from the Longitudinal Study of Young People in England, an EMA payment of £30 per week is found to reduce teenagers’ labour supply by 3 h per week and probability of employment by 13 % points from a base of 43 %. We conclude that parents withdraw cash and in-kind transfers from their children to a value of between 22 and 86 % of what the child receives in EMA. This means we reject the hypothesis of an effectively altruistic head-of-household, and argue that making this cash transfer directly to the child produces higher child welfare than if the equivalent transfer were made to parents

Tumor fibroso solitario de la pleura

El tumor fibroso de la pleura es una neoplasia poco habitual cuya presentación clínica es inespecífica, obligando al diagnóstico diferencial con otras patologías respiratorias más frecuentes. El diagnóstico definitivo es histopatológico. Su tratamiento es quirúrgico y debe realizarse seguimiento a largo plazo por la posibilidad de recidiva. Se comunica caso de una paciente portadora de un tumor fibroso de la pleura, que se manifestó por dificultad respiratoria, dolor torácico y signología clínica de ocupación pleural. El diagnóstico se determinó mediante biopsia por punción percutánea del tumor. La paciente fue sometida a toracotomía exploradora, realizándose extirpación completa del tumor, con buena evolución postoperatoria

Haemodynamic consequences of changing bicarbonate and calcium concentrations in haemodialysis fluids

Background. In a previous study we demonstrated that mild metabolic alkalosis resulting from standard bicarbonate haemodialysis induces hypotension. In this study, we have further investigated the changes in systemic haemodynamics induced by bicarbonate and calcium, using non-invasive procedures

Pass/Fail, A-F, or 0-100? Optimal Grading of Eager Students

This paper analyzes optimal grading in a world that focuses on top grades. Students choose an effort level, their performance is graded, and their grade correlates with their future income. Ex-ante, the policy maker chooses the optimal coarseness of the grading scale to maximize student welfare. When choosing their effort, students overweight outstanding - or salient - grades. I show that this behavior leads to excessive effort levels when grading is fully informative, and that coarse grading can be used to counterbalance incentives. Thus, salience can help explain why grading ranges from Pass/Fail scales (tenure decisions) via A-F-scales (school) to fully disclosing scores (e.g. SAT)

Color-Coding Improves Parental Understanding of Body Mass Index Charting

To assess parental understanding of body mass index (BMI) and BMI percentiles using standard versus color-coded charts and investigate how parental literacy and/or numeracy (quantitative skills) impacts that understanding

Hysteretic magnetoresistance and thermal bistability in a magnetic two-dimensional hole system

Colossal negative magnetoresistance and the associated field-induced insulator-to-metal transition, the most characteristic features of magnetic semiconductors, are observed in n-type rare earth oxides and chalcogenides, p-type manganites, n-type and p-type diluted magnetic semiconductors (DMS) as well as in quantum wells of n-type DMS. Here, we report on magnetostransport studies of Mn modulation-doped InAs quantum wells, which reveal a magnetic field driven and bias voltage dependent insulator-to-metal transition with abrupt and hysteretic changes of resistance over several orders of magnitude. These phenomena coexist with the quantised Hall effect in high magnetic fields. We show that the exchange coupling between a hole and the parent Mn acceptor produces a magnetic anisotropy barrier that shifts the spin relaxation time of the bound hole to a 100 s range in compressively strained quantum wells. This bistability of the individual Mn acceptors explains the hysteretic behaviour while opening prospects for information storing and processing. At high bias voltage another bistability, caused by the overheating of electrons10, gives rise to abrupt resistance jumps